Question 139950
First, we need to find the missing angles of each triangle. 



For the first triangle, first add up the two given angles 69 and 48 to get 


{{{69+48=117}}}


Now subtract 117 from 180 to get


{{{180-117=63}}}



So the first triangle has these angles



<a href="http://s293.photobucket.com/albums/mm56/cool_user2004/?action=view&current=5a.jpg" target="_blank"><img src="http://i293.photobucket.com/albums/mm56/cool_user2004/5a.jpg" border="0" alt="Photobucket"></a>




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For the second triangle, first add up the two given angles 63 and 48 to get 


{{{63+48=111}}}


Now subtract 111 from 180 to get


{{{180-111=69}}}



So the second triangle has these angles



<a href="http://s293.photobucket.com/albums/mm56/cool_user2004/?action=view&current=5b.jpg" target="_blank"><img src="http://i293.photobucket.com/albums/mm56/cool_user2004/5b.jpg" border="0" alt="Photobucket"></a>




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For the third triangle, first add up the two given angles 63 and 48 to get 


{{{63+78=141}}}


Now subtract 111 from 180 to get


{{{180-141=39}}}



So the third triangle has these angles



<a href="http://s293.photobucket.com/albums/mm56/cool_user2004/?action=view&current=5c.jpg" target="_blank"><img src="http://i293.photobucket.com/albums/mm56/cool_user2004/5c.jpg" border="0" alt="Photobucket"></a>




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Summary:




So the three triangles have these angles



<a href="http://s293.photobucket.com/albums/mm56/cool_user2004/?action=view&current=52.jpg" target="_blank"><img src="http://i293.photobucket.com/albums/mm56/cool_user2004/52.jpg" border="0" alt="Photobucket"></a>




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Answer:



Remember, similar triangles have equal angles. From the figure, we can see that triangles a) and b) have equal angles. So triangles a) and b) are similar triangles.